if the universe started from big bang and the speed of expansion is speed of light how can we see back in time

Question

If we started from a point (say a working clock face reading 12:01am) and raced away from that point (say because of THE big bang) at less than the speed of light, how can we look back at the clock and hope to see what it looked like at 12:01am (that is the big bang)? That is although the clock will appear to be running slower (for as long as we can see it), it doesn't stop because we are travelling slower than light away from it.

Can you please explain it like you might to someone whose knowledge of science doesn't extend beyond what we learnt at juniour high school?

that is say we are moving away from the big bang at 1mph and have always been moving away at 1mph, then wouldn't all of the light from the big bang have wizzed past us already?

that is once it is past us how can we look at it?

Answer 1

The universe expands at what is called the hubble constant. Basically let's take a measurement and pretend we know the exact rate of expansion, say a light year. Lets pretend space expands so much in a lightyear, let's say a centemeter per week. Something one lightyear away will move away from us at one centimeter per week. Something two lightyears away will move at two centimeters per week. The further you look, the faster things seem to be moving away from you. This effect can be seen until something is so far away that it seems to be moving away at near the speed of light. The smaller a distance between two objects, the less the expansion of space moves them further away from each other. The more space, the more the expansion will move them realtive to each other. This is why we can see things since their speed depends on their distance from us.

Answer 2

First...

a light year is measuring the distance that light travels in one of our years.

So a star that is very, very far away sends out its light but it will take a long time to get to your eye even traveling at the speed of light. Astronomers call it light years. The light occurred from the star millions of years ago but it finally reached your eye. Since the light is millions of years old, it is the same as seeing into the past.

If you were in a trolley leaving a village and looked at the clock , as you were able to get the trolley to go faster and faster the clock would seem to slow down. You are able to see the clock because your eye send an image of reflected light from the clock, As you go faster, nearing the speed of light, you begin to catch light the that was reflected making the clock seem to be slowing and as you go faster (if possible) you see the clock hand stop because the light is traveling with you . This mind experiment allows you to imagine passing the light and catching the earlier reflected light and the clock hand would appear to be moving back. It is supposedly impossible to physically not possible to do this but it may be possible by squeezing the space instead of increasing the speed.

Instead of moving the trolley, roll up the track by bending space/time.

It all become more curious at this point. Multiple dimensions / paradoxes , worm holes.

Read a "Wrinkle in Time" for an enjoyable explanation.

Below is a link to what Professor Mallet has been able to do using a rotating laser beam. Time travel will happen someday.

It may already exist (but of course if it really does then time travelers might be here already)

Answer 3

It is necessary to understand the nature of dimensions if you are to understand the workings of the universe. Any object moving perpendicular to any other object is said to be moving in different dimensions. This can be shown graphically on a piece of paper just using X and Y coordinates. X is recognized as one dimension and Y as another.

Dimensions have real world relations. If you move an object in the spatial dimensions you can only have three directions, dimensions, that will have no change of position or resulting action of a force.

From observation we see that there is uniform redshift from distant objects in all directions of space. This red shift can only be the result from motion in a direction that is perpendicular to all spatial directions.

We also know from observation that the universe started from a single point and is expanding outward. The start of this expansion is called the Big Bang.

From the two observations it is clear that the transition outward from the Big Bang is not in a spatial direction, dimension, but is in a direction that is perpendicular to all the spatial dimensions.

The only thing we know that can limit the rate of transition is the natural limit of the speed of light. This is not out of line with other observations. The redshift numbers are of this magnitude and gasses moving away from exploding stars approach this speed. We are even able to move particles at close to the speed of light.

As to the question of “why are we able to see what we do”.

In a system where all things are moving at the same rate objects or waves that move between two objects in that system continue to move at the same rate in the Big Bang expansion direction at the same time they are moving in the spatial direction. The time it takes to move between to objects moving outward from the Big Bang is only dependent on the spatial velocity and the spatial distance between the two objects.

If you give this ability careful thought you would see an important relationship between independent dimensions.

Answer 4

I don't quite understand your question, but I'll try to answer it.

When you say "see", you are talking about light. Our eyes can only see things by the light things produce or reflect. When we say we can see back in time, it means that the light reaching our telescope from another galaxy billions of light years away -- that light is billions of years old. Maybe that galaxy looks a lot different now or isn't even there anymore. But the light reaching our telescope shows what that galaxy looked like billions of years ago.

Time is a very flexible thing, and it is wrapped up inside of the fabric of space like ice cream in a blender.

One of the misconceptions about the Big Bang is that it resembled the explosion of, say, a hand grenade, with shrapnel going in every direction away from the point of explosion. While this certainly gets the idea of the expansion of space across, it is misleading to think that the Big Bang happened "somewhere out there." It happend where you are, where I'm sitting, and it happened 14.5 billion light years from us. There is no "center" per se.

Your question is hard to explain in simple terms, there are many books on cosmology if you are interested. The thing I would like to get across is that the speed of light is not a barrier to the speed that the universe can expand. Light speed is the speed limit for light, not for the expansion of space.

So, to get back to your question, our visible "horizon" is about 14.5 billion light years in any direction. This is why a current estimate for the age of the universe is about 14.5 billion years.

There is a strong connection between time, space, and the speed of light. When we see a quasar (huge galatic-sized ball of energy driven by a black hole at its core), that quasar is in an area of space maybe 12 billion light years away from us, because quasars exist(ed) in the early universe. We do not detect any quasars nearby, not until several billion light years away. Light left that quasar 12 billion years ago to finally arrive at our telescope. Yes, if I understand your question, you do have to take into account that when the light left that quasar, the universe was much smaller and everything was closer together. That is referred to as "look back" time, but the point is, it is the space in between everything that expanded, not the quasar or our galaxy our our solar system. Empty space got larger. Light still chugged along at its constant speed.

You see Rigel (a bright star in Orion) as it looked 6 years ago.
You see the sun as it was 8 minutes ago.
You see the moon as it was 1.34 seconds ago.

Amazing stuff, thx for the question.

Answer 5

Hi. Assume that the expansion WAS at the speed of light. (Not really possible because of the infinities it presents, but let's say.) Objects at the 'edge' would be frozen in time. They move away at the speed of light (in our hypothetical example). The farthest we could possibly see would be the distance that light could have traveled since the bang. If we could see a clock at that distance, and it was frozen in time, and it froze at 12:01, then what would you expect to see?

Answer 6

The universe is not expanding at the speed of light. If that were the case, we would not be able to see anything changing. The speed of light is greater than the speed of the expansion, so that old light rays from stars are catching up to us now and we can see them go nova, etc.

Answer 7

The universe is not expanding at the speed of light.

When we look out into the universe, we are seeing light that left stars and galaxies years ago, sometimes billions of years ago, to reach us. The oldest light we've found (the cosmic microwave background) is about 13.7 billion years old.

Answer 8

technology has generic the existance of an clever clothier...first of all. 2d of all, quicker than the fee of light may be the fee of light plus it is very own acceleration,no remember what brought about the acceleration. third, this is a paradox, using fact there are people who say quicker than the fee of light skill backward in time, which may be one extra element on account which you will possibly get there formerly you left and in terms of the large bang it would have finished formerly it began. there are a number of large paradox...in case you like them shop examining them.

Answer 9

The big bang is not at the speed of light, that is where your reasoning goes wrong.

Answer 10

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