Frozen in Time?

When we observe the Universe, we are looking back in time. We see it how it was, not how it is. What are light-travel time effects?
A lecture by Katherine Blundell OBE, Gresham Professor of Astronomy
23 October 2019 1PM BST
www.gresham.ac.uk/lectures-an...
Most information from outer space reaches us at the speed of light and this governs our understanding of time and evolution in the cosmos. When we observe the Universe, we are “looking back in time”: we see the Universe as it was, not how it is. This is actually very helpful as we seek to discern and understand cosmic history and how the Universe has changed since earlier times.
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[@CosmosMarinerDU]

What a beautiful voice she has.

[@whirledpeas3477]

Listen @ 1.5 speed ❤

[@swenic]

Night sky could be dark cause of dust, and reversing the expansion might result in evenly distributed matter.

[@ianp3112]

The question regarding the fact that at night the sky is dark! But isn't that only a human limitation, we can only see the visible part of the electromagnetic spectrum. If we could see radio waves, microwave, infrared, x-ray, gamma rays, aka the entire electromagnetic spectrum, would it not be just as bright as daytime?

[@brainstormingsharing1309]

Absolutely well done and definitely keep it up!!! 👍👍👍👍👍

[@jfffjl]

Space and time are manifestations of the same thing, and the faster you go in space, the slower time goes where you are. So is there a law of conservation of time?

[@sarahclemans4772]

Does anyone have link to the lecture on dark matter and dark energy that she mentioned?

[@tweakp0si0n]

Tldr; Yes.

[@PaulHigginbothamSr]

At the event horizon of a black hole time is frozen. This leads to strange consequences when two black holes collide. It leads to failures of logical thought that cannot have a past and future events. We know they can collide thus producing these failures of one event preceding another and have logical inconsistencies. The happenings are thus out of time sequences and thus reality failures which obviously follow outside reality not included as either motion or causality. These breakdowns seem to preclude reality following causality and thus local areas failure of reality.

[@vladimirp2674]

Each time i looked at the night sky, each time it holds me and puzzled me more, i never stop to think what a huge scale it has and how small i am regarding to the spectacular beauty of it. The knowledge is infinite like the space. And more we discovering, more questions appeared. Is it more safe to stay ignorant, is't it?

[@CandidDate]

Why the stars don't change? Almost as if, .... as if.... as if ..... we're special.

[@stadsratify]

Earth-moon 3 seconds?

[@marc-andrebrunet5386]

🎯Same reaction! It's probably a mistake because in general, we all learned that it's for a📡 signal to go and come back and so on.. Funny cause my eyebrows went down at this moment.. 👉And if you find, there is another funny mistake somewhere..i don't remember when, maybe 3/4 of this excellent lecture📝

[@speculawyer]

Yeah, that's wrong. That's close to the roundtrip time rounding up. ¯\_ (ツ)_/¯

[@Tom_Quixote]

Yeah I thought the same. How strange that this expert would make such a basic mistake.

[@brownj2]

Why oh why do all these astronomy lectures assume ignorance of such simple things like doppler shift? Honestly how many times do you need to explain some of the most obvious things in the universe?

[@alexcastro7339]

Every decision you ever made in your life brought you to this comment to read it, right at this time and place. How was your journey so far?

[@marc-andrebrunet5386]

📈Not bad, a good mix of KZbin learning stuff and📴 many hours in Real Life with family members outside my "stressful city"✌

[@jamesdolan4042]

alexcastro7339, I'm a man of no importance. How about you? Sorry, your comment is not a singular life defining moment for me.

[@alexcastro7339]

@@jamesdolan4042 Try obtaining a sense of humor. 😉

[@paulwainwright4100]

¹