I read that the Hubble telescope could look 13.2 billion years back in time – what would it see if it turned 180 degrees and looked the other way?
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Everybody is the center of the universe due to how it expands universally. If I were in another galaxy looking somewhere, what I saw would show me as in the center of the universe and what you saw here would show you as in the center of the universe.
There’s a fixed limit to what can be seen by any telescope so if the Hubble points in one direction it’ll see a certain amount of time into the past and if it points in the exact opposite it’ll see the same amount of time in the past.
There is a caveat though due to things like gravitational lensing. If you find such a lens effect, then you can see further away than you normally could and therefore further into the past. This requires a very specific alignment of galaxies and dark matter between you and the object on the other side of it. If you’re referring to this effect as the limit, then the time you can see into the past differs based on how strong the effect is and where it’s located. Different lensing effects magnify what’s behind them differently so you aren’t guaranteed to see the same timeframe into the past with every lensing event found.
‘Back in time’ is not in a physical direction. The Hubble telescope can see things as they were many years ago, because that light has taken a long time to reach us. It would be like if your friend went to a distant city and took a photo and then brought it back to you two weeks later. The city in the photo is how it looked two weeks ago, not how it looks right now.
Yes.
The universe is expanding in all directions at the same time. To get a sense of what this expansion is like, put 3 marks on a balloon. Then, blow up the balloon. As the ballon is filled, each mark becomes farther away from the other marks.
Yes. You would be. However, you will not be able to see it because of doppler effect. As universe has been expanding at very fast rate, the light that was emitted during big bang has also stretched out. The stretching of light means increasing wavelength in the micrometer range. So the light would be a Microwave.
Since at the beginning the universe was completely concentrated at a single location with very high density, and it expanded in all directions, we see uniform image across all directions.
Sine the waves will be MICROWAVE, distributed uniformly EVERYWHERE throught the COSMOS it is called Cosmic Microwave Background (CMB).
So besides being large, the telescope will also need to be able to detect microwaves.
Because light does not travel instantaneously and has a speed limit (C), no matter which direction you point your telescope, it will always view objects as they were in the past. And the further away you look, the further into the past you are looking.
For instance, when you view the moon at night, you are actually viewing the moon as it was approximately 1.3 seconds in the past. When we view mars through our telescopes or if you spot it in the night sky, we are seeing as it was between a 3-13 minutes in the past, depending on the relative orbits of Earth and Mars. And when viewing the closest star (Proxima Centauri) to our solar system, we are viewing it as it was more than 4 years in the past.
So, you can extrapolate from there, and see, that if you continue to move further away in your observations, you will continuously peer further into the past, irrespective of the direction you are looking.
In fact, if the sun spontaneously exploded or extinguished itself, we wouldn’t even know it happened until 8 minutes after the fact. We would simply look up and see the sun, without noticing any difference whatsoever. Kind of fun.
ELI15: In fact, the latest measurements of the curvature of the universe suggest it is flat (and infinite) and there is no preferential point from which the universe expands. This means the observable universe from earth, the entire universe from our perspective (90+ billion light years diameter, due to inflation), is just one in a likely infinite set of observable universes, all of which, aside from our own, we will never be able to access. And even within our own observable universe, assuming we could travel at light speed, we would still only be able to visit approximately 6% of what we can observe, due to how fast everything is moving away from us.
So here is something that needs to be explained so that you kind of get a better picture of what’s going on. When you use a telescope and look “back in time”, it’s not really looking back in time as people would think. Saying you’re checking out a star 5 billion light years away. What you see in the telescope the light given off is 5 billion years old, as that’s the time it took the light to travel to you. That’s why they say you are looking back 5 billion years.
Something like the Hubble telescope has the ability to look further than your standard telescope. The further you can look the further these objects are away which means the light takes longer to reach you.
There is no need to do a 180 degree turn to see the other way. The telescope orbits the earth going round and round, and it’s always pointing outwards. So it’s constantly working to give us a 360 degree view. Think of it like putting a camcorder on a lazy Susan and then spinning it. You’ll get a view of the room 360 degrees on the axis of the lazy Susan.
So turning the Hubble the other way would pretty much just show us pictures of earth honestly lol.
As far as whats out there? Basically the universe is expanding at a rapid speed. So it’s not like we will ever be able to see the edge of the universe. So whatever we see through the telescope is the light being shot at us from that direction. We have no way of seeing what is past the edge of the universe.
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No matter which way you look, you will be looking into the past.
Everything you see in front of you, you see as it was at some point in the past. It takes time for the light from any object to reach your eye.
Say you’re looking at a computer monitor 24 inches in front of you. (using mine as a measure).: The speed of light is ~186,000 miles per second. So it took the light from your monitor ~2 nanoseconds (2 billionths of a second) to reach your eye. You’re seeing it as it was 2 nanoseconds ago.
You see the moon as it was 1.3 seconds ago.
You see the Sun as it was over 8 minutes ago. It could have exploded 4 minutes ago and we will not know it for another 4 minutes.
The further distant an object is, the older the light reaching your eyes from it.
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Many people misconstrue the Big Bang and think of space as an empty room and the Big Bang as an explosion that then fills the room.
A better interpretation is that the room itself was very small and then the Big Bang happened and the room has been expanding every since.
So when you take your telescope and look in all directions, you’re seeing different parts of the room. But all parts of the room were once all at the same point at the instant of the Big Bang. So no matter where you’re looking, you’re looking at the Big Bang.
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