"Dark Energy = Dark matter * (Speed of Dark)^2" got me laughing for much longer than I should have

Whether you use standard candles or cosmic microwave, your frozen burrito is still going to have a great cold spot.

I get soooooo excited when there’s an argument between prediction and observation at this level - because it means we are missing something. And that means more science! MORE SCIENCE! 😁👍

A decent treatment of this outstanding problem in current cosmology... not too overly detailed, clear, and thorough ! Great job !

we could just cut the photons in half and count the rings

*An engineer walks in* Just take the average of the results and call it a day...

"We know everything, as long as we can prove this number is constant" "... damnit."

7:41 subtitles say "are a factor of 100,000 cooler", but actually 1/100,000. A mere 10 orders of magnitude wrong :)

I love to imagine what PBS Space Time will talk about 20 years from now, seeing how much questions about space time still haven’t been answered ^^

That's great. It may means that we are wrong about something and need to rethink things. And that's a great opportunity for us to discover what is wrong, but also to consolidate what's right.

Socrates: Shall we set down astronomy among the objects of study? Glaucon: I think so, to know something about the seasons, the months and the years is of use for military purposes, as well as for agriculture and for navigation. Socrates: It amuses me to see how afraid you are, lest the common herd of people should accuse you of recommending useless studies. - Socrates

Thank you PBS and Matt! This is one of the most enjoyable and informative shows on youtube and anywhere else. I'm fascinated by astrophysics and these episodes only help to raise my interest until I can start taking these courses for my degree.

Man I'm smart. *watches PBS video* Man I'm stupid.

The Hubble . . . variable?

Well the answer is obvious isn't it? Hubble Constant = 42

I love when you say things are easy.

Why did this get taken down for like 30 minutes? I was watching and it was just deleted from existence. Am I a time Traveller?

The Crisis in Cosmetology

I need to get the BGM for these episodes. They are so calming and great to listen to while having a learn

This is the most profound video I’ve ever seen on this channel, thank you for the curiosity :)

Not so constant now, eh?

A shame y'all didn't take the opportunity to recognize Chandrashekar who did the math to figure out the critical mass that makes IA supernovae luminosity so highly predicable--and for whom the Chandra X-ray telescope was named for.

This so very exciting.

Wonderful show! I thought you had run out of subjects. I was sooo wrong. You have surpassed Gabe. Incredible feat!

I think it's fair to say the calculation based off the CMBR relies on more assumptions than that of Type 1a Supernovae.

Best part of the week! I love this channel

He does a remarkable job of explaining the topic. Thanks

This is great and exactly what I’m doing in my undergrad right now. I’m basically listening to my report, laid out much more nicely

*_Einstein's cosmological constant has joined the server_* *_Hubble's constant has joined the server_* *_Einstein's cosmological constant has left the server_*

I really do wish you'd include links to the papers you cite.

I've just seen the Joe Scot's video on quantized inertia and it got me hooked. Please do a video on the subject. I'll do some reading in the meantime so I'm ready for your in depth suff when you get around to it.

Your lectures enter in one ear and go out from another

I like how you gave credit to Vesto Slipher, Hubble usually gets the credit for red shift measurement

Oh it's back! I thought the crisis was over, But I guess it's back again.....

What I love most about these shows is that it allows for understanding to be both mathematical and hypothetical! Allowing for the furtherment of... Spacetime...

This is such a great channel!

I finally know what he was trying to say 0:22! I was so lost, was it Uniform, was it University? Unibomber? Uniqlo? Who knew? Glad that mystery is finally solved.

Perplexed: if light from distant galaxies travels to us longer, that means they are older than the near ones. So if far away ones recede faster than near ones, doesn’t than follow that in the past they receded faster...?!

The cosmological constant is not constant. It seemed constant because we have only one/two data points when we describe the observable universe scale. There are dynamics in the observable universe scale, just as with any scale, and new forces, etc. All we can get are >effective< field theories. We should embrace it.

It amazes me that despite constant failure to find any dark matter/energy signal in any experiment, it's still firmly rooted in the mainstream as absolutely correct.

Question: Does the Local equation assume it starts from a singularity? What if it didn't? How big would the initial universe need to be to make the two equations align?

The best channel, IMO, on KZfaq. Perhaps the whole universe is a vast fractal pattern operating with a Heisenberg uncertainty principle. Or it's a vast living organism. I always feel like I ate a ton of shrooms after watching these videos. Thanks for the great videos!!

PBS has always been the Unknown Soldier!

I love how this channel doesn't dumb things down!!

Gravity Waves - Nature of the Speed of Light, Dark Energy and Dark Matter - Musings of the most dangerous type - with only partial knowledge. Listening to Dr. Krauss on Penn’s Sunday School talking about gravity waves got me thinking. The fact that gravity waves have now been shown to exist, this seems to have some interesting implications to me. I admit that the following thoughts have probably been thought of by smarter minds than mine, especially since my degrees are in Geology and Planetary Science with a minor hybrided between Physics and Remote Sensing. However, in listening to this I was using the following hypothesis and was predicting what some of the possible reasons for the differences in H naught could come from, specifically Dark Energy not being constant. Gravity waves are the physical effect of the movement of mass through space-time. To me this may help explain the speed of light and the difficulty of reaching it. If a gravity wave is created every time a mass moves, and given that presence of a mass of matter will bend space-time, then moving matter not only should create gravity waves, but try to drag the frame or fabric of space-time with it. The faster a mass tries to move the more it drags on the frame or fabric of space-time. This drag then would act as a form of inertia that increases as velocity increases. This would explain why you need a nearly infinite amount of energy to accelerate a mass of matter to the speed of light. It also may explain the speed of light itself. Many experiments exist that demonstrate the duel nature of light, particle and wave. Classically, the mass of a photon of light is essentially zero. But what if it really isn’t? What if the mass of light is infinitely small, say one divided by a googleplex, with the result raised to the power of a googleplex. And it is the mass of a photon of light that limits its speed to the speed of light because of the gravitational frame drag inertia created by the moving light. IF true, then light, as it moves through the universe is attempting to drag the fabric of space time with it. With light literally moving through the universe in every direction, could light be responsible for stretching the fabric of space-time through a drag force? Would that mean that it is the frame drag of light that is what we call Dark Energy? As the fabric stretches, in all directions, then the light energy fills it out again, keeping the universal constant energy density. Conversely, we know that matter warps space time towards it. But we also know that we see gravity as being too weak. Could it be that the force of gravity is, in part, dissipated in fighting the frame drag expansion created by light? Could it be that Dark Matter is not an exotic form of matter, but the effect of gravity on the fabric of space-time? If true, then if we could minutely measure the amount of red shift due to expansion of the Universe, then it would seem that the amount of expansion, and hence the amount of red shift should differ for say the area around a star in intergalactic space, and stars orbiting close to a galactic center super massive black hole. This would seem to explain some, if not all of the difference as you would need to consider a variable of energy density between us and the object being measured to determine H naught.

"Speed of Dark" lol

Cosmology should distinguish between those two different statements: 1. "Redshift is proportional to distance". 2. "Further galaxies recede faster away from us." Statement 1 is an accurate, experimentally backed statement. Statement 2 needs a bunch of approximations from statement 1 to be made..... including that redshift is ONLY made of Doppler effect.

A crisis in cosmology! Hold on! Saving to "watch later" playlist because I need to call some friends and get some beer for this!

how different would the inputs in the CMB modeling have to be to get a result from the other method? has anyone considered this approach?

This universe could not contain the amount of information of this video so they had to compact and reupload it

Best series on KZfaq

Thank you Matt !

Do you think you could ever do a video on “Iron Stars” which Isaac Arthur talked about as the final future of stars if protons don’t decay and the “Big Rip” doesn’t occur

Can you explain why we're so hung up on the notion that dark energy has remained constant since the release of the CMB? You mentioned the possibility of variable dark energy almost in passing, but considering how little we actually know about it, this seems like a rather simple theoretical explanation for the discrepancy in measurements.

this is just mind blowing

You are our every eye and ear to what our brians needs to understand

If the Hubble Constant is the rate of expansion of the universe, then wouldn't it be evident that the Hubble Constant in the distant past would be significantly smaller then than it is now since the rate of expansion is accelerating? What if both values are correct?

"The velocity part is relatively easy" Pun intended?

Sup? Thank you PBS and Dr. O’Dowd for another great episode of... ...Space Time!

Awesome video!

Just had a Déjà vu..

Now we have to measure the speed of dark !

Anton Petrov recently reported on new studies showing that the "constant" is not constant at all

This may be the best expansion video available. Thank you. I feel that the expansion of space should change certain things like electron flow, mass. And a thought that just occurred to me is, could space at near the limit of expansion get weak and cause a tear in a gravity well? Also, i feel redshift interpretation is not completely uniformly accurate and if we can resolve that, we may solve a few issues.

It makes me sad that there's a universe where I'm a crackhead and my parents are crying, wondering where they went wrong

I have much greater trust in the directly observed supernova measurements.

I noticed the use of megamanX4 music in the background of this video and i compliment your choice.

Great video

Where can I get the shirt you're wearing in this vid?

It would seem that the "constant" would prefer to be a variable.

I like listening to these vids because it make me feel smart, even though it's all over my head :-)

there can also be "an unknown event happened and interfered with the thing", rather than just "this event we know interacted with the thing differently than how we think it did"

Negative mass would be interesting. Personally, I really want tachyons to exist. That way the universe would have particles with imaginary mass.

wait wait wait... the universe was playing a sound when it was opaque...? that's soooo cooooool... _the song of the baby universe_ (cry?) nice...

Dude I love your show

The H0 is quite important! But I think James Webb might give one of these teams a little edge. Gravity waves might have the answer. Exiting times ahead of us.

I enjoy these videos, but they make me feel dimmer than a brown dwarf, sometimes.

Let's be totally honest here: what are the odds that the accuracy on these competing calculations is just not as good as the scientists want to think? Especially with that second method, there must be so many variables baked in that I really struggle to believe a +/- 1% accuracy.

Your blinding me with science!

09:14 "How do you get the Huuble Constant from all of this ?", i think that question overshadows the work that must have gone in to actually find out the answer deemed as "All of this" , i for one was "blown away" , by "All of this" , when he explained about the battle beween light and gravity it made me soooo thankfull that im alive in a time where information is just a "click" away ! ! !.

Another reason for the crisis in Cosmetology is that there aren't enough qualified Aestheticians

A red shifted photon has less energy than if it is not red shifted. Assume concervation of energy, where does this energy go? If i throw a ball strait up, Kinetic energy is converted to potential energy. If redshifting photons is converting kinetic energy to potential energy, what does this mean on a cosmic scale? And if there is no effective way to converr that potential energy back to kinetic energy, does that change our notion of conservation of energy in regards to the universe?

That background space image is an image of the space surrounding the star Rigel. I just realized that. Nice.

Cool story Bro, but Halton Arp has another theory, one which radio astronomy seems to confirm more than the expanding universe concept. That is the redshift of galaxies is proportional to the "age" of said galaxy or quasar. Quasars and galaxies have been seen linked via plasma channels (Birkeland currents) thanks to radio astronomy. These connected galaxy-quasar groups show that obviously the quasars we once thought were so far away are actually closer than we thought, and that it may be said these quasars were "birthed" by the galaxy its connected to through these plasma filaments. Check out Thunderbolts Project on KZfaq for videos relating to how astrophysics truly is in crisis as it flails about trying to create crazy objects and explanations for things using only gravity as the prime motive force in the universe.

We expect other galaxies to be all moving away at exactly the same rate, but if our current model is wrong then we might observe slightly different rates. For example, if massive objects in space are free falling in 4 dimensional space (5 dimensional space-time) then depending on the mass and how close it was to other massive object(s) when it's mass became significant enough to fall away instead of fall towards another massive object, and many other potential factors, objects could be moving away from each other at slightly different rates. It is also possible that space isn't expanding then, and all massive objects are free falling in 5 dimensional space-time.

I thought that parsecs was just an average sexual encounter between two golfers.

That’s one of your best..,!

Hi here!!! I don’t actually comment...but am sooo amazed of ur channel (its z best )....but i would really like if u made a video about “fringe theory” ...am sooooo exited to see that (cuz obviously no one can do it better than u ).......am waitin ....peace!!

What about a direct measurement of the Hubble Constant? I know that sounds silly at first glance, but it's not strictly impossible: In the last 40 some years the Voyager 1 space probe has been flying away from us, it should now be about 2 cm further away from us, due to the tiny sliver of space between us expanding during that time, than if space was not expanding. This is tiny on an astronomical scale, but a readily understandable and measurable distance. Though we know Voyager 1's position and velocity relatively well, all things considered, it's not nearly precise enough for that sort of measurement. But it should be possible to construct an experiment that would be capable of measuring the infinitesimal additional acceleration we would observe of a space probe flying away from us on a human timescale, and not only from analyzing million-year-old photons.

what about h0 calculations by the gravitational waves?!!!!!

On the off chance that you see this, would you be interested in revisiting this topic with the recent reports from the CCHP regarding the tip of the red giant branch stars? I just had to do a report about the crisis, and I found their paper really interesting but I don't think I know enough to weigh in on its accuracy

I still watch this channel despite having 90% go over my head.

Dark energy is the fish trying to decifer how gravity affects tidal waves without yet knowing about the existence of water .

Pop Cosmologist: "80% of the universe is made of 'dark energy' and 'dark matter', and we don't know what it is - nor do we know the exact rate of it's expansion" "But we CAN describe the exact state of the universe at each fraction of a second after the big bang"

hmmm, I love that channel even if I usually cannot follow anyway. this time I thought - what about the for me 'obvious' possibility that the hubble "constant" is changing over the long long time...? I was surprised that this possibility was not mentioned.

Interesting !! Maybe a presentation on the Janus Model and the last paper of authors on QM ? Seems to propose interesting facts to be confirmed in this context...

Could you explain the significance of the Hubble Ultra Deep Field?

Why do cosmologists talk about the "moment" when the CMB was released, when the hotter denser regions of the universe must've taken longer to cool enough to release their CMB radiation?

can you do an episode on the amplituhedron and why scientists are interested in understanding scattering in the first place? why are physicists so excited about the amplituhedron? big fan!!!!!!

I am no cosmologist but my money is on dark energy being the fly in the ointment, given that one of the possible sources of it is the expansion of space itself. Its interaction with the universe may have been substatialy less in the early, CMB era than it is now. Just my guess anyway.