😂

YES!

Mine too. 🥰👍‍‍

Is that a problem?

@@jiversteve no, but that would make it even more interesting to ask it to people in other fields!

@@1draigon Would a biologist have anything to add? The scientific community is not as insular as you seem to think!

@@jiversteve not a biologist. But he is very much particle focused! String theorist for example would have different wishes

@@1draigon Any physicist would already be on the case. Bye for now.

He really is delightful. Understands his audience well and unravels the intricacies of the topic with such patience and grace.

I really wish there were full-length lectures available from him. I love cosmology, but, really, I could listen to him lecture about lawn furniture 😂

There is a video about super strings with Ed. It's a couple of years old now. Would love an update though!

and nicknamed the Jelly Welly Space Telly

I think dark energy is, ironically, just the Energy that light is dumping into the space it traverses, causing it to expand.

the key concept is energy density

In GR, the notion of “energy” is rather delicate. Sometimes people say the expanding universe doesn’t conserve energy, but what they mean is that if you add up the energy of everything that contributes to the universe’s _energy density_ (namely matter, radiation and dark energy), then the energy is not conserved. However, this notion of energy doesn’t include contributions from the spacetime itself! If you also add the energy of the spatial expansion and curvature, then you find that the energy is conserved. The second notion of energy is more complete, since it takes everything dynamical about the universe into account, but there is a slight difference between this notion of energy and others you see outside the context of GR, which is that you have to very carefully define what “time” actually is in a curved spacetime, since energy conservation is canonically related to the laws of physics of a system not changing with time. Once you appropriately define “time”, you can then ask what the spatial curvature is at each instance of “time”, and it is essentially from this spatial curvature that the spacetime energy is calculated. Luckily, the geometry of the expanding universe’s spacetime is such that the “time” we can use is simply the ordinary time we are used to, since the only curvature the model of the expanding universe contains is purely spatial curvature.

You do see one image from each galaxy corresponding to its distance (leaving gravitational lensing aside). The younger light did pass us already. The older light is still on the way.

You cannot see the same galaxy at different epochs, at least not in the human timescales that is being considered in the video. What we can do is, look at distributions and structures of galaxies in general at different points in times and try to understand the evolution and the structure of the universe as a whole.

@@burnere633 Technically it is possible for a large enough black hole to twist the light around and make the light from the same galaxy turn around and arrive later than the light that's coming directly from that Galaxy, and depending on the placement of the Black Hole and the Galaxy, it might have a separation of epochs indeed.

Supernovae create white dwarfs, not the other way around. The stars that created red giants that became supernovae are short-lived - the larger and hotter, the shorter. Then white dwarfs are the long-lived remnants. Edited I've heard what Ed said. I may be wrong but I think he may have misspoken.

@@PopeLando type 2 supernova creates white dwarfs, type 1 destroys them. White dwarfs are remnants of lower mass stars which tend to have a lifespan of billions of years. In the early universe, how is there enough time for white dwarfs to form?

Retreat

Less than logical person, you fill in the gaps!

It’s been hit since the beginning of our time, why should it stop in our time?