# What is the edge of the universe like? Is it a brick wall or what? Will we be able to go past our universe someday?

#### Too bad it's not a brick wall or something like that. Actually, there really is no "edge" of the universe so we can't go past it. There are two cases that could happen. One is that the universe will expand forever. This means that the universe is infinite in size so it doesn't have an end. It just goes on and on and on. The second case is that the universe will end in a Big Crunch. In this case the universe is finite in size because of gravity. So if it's finite in size, why isn't there an edge we can go to? That's because of a weird little thing gravity does to space--it curves it! Einstein first came up with the idea of gravity curving space. That's how the Earth orbits the sun. It wants to go straight but the Sun curves the space around it so the Earth can't go flying off. There is so much matter in the universe that space is bent back on itself! It's sort of like how you can bend a wire until its ends touch, you come up with a circle. You can walk around a circle forever without coming to an edge. So, the universe can be finite but have no edge. It's similar to the Earth. The Earth has a finite surface area but it doesn't have an edge that you can fall off (lucky for Columbus...)

Submitted by Lance (Utah, USA)
Submitted by Brent (Tenessee, USA)
Submitted by Alyssa (California, USA)
(August 21, 1997)

## What are the retrograde motions of planets in the sky?

It depends on which type of motion you are asking about. If you take a birds-eye view from the top of the solar system all the planets orbit around the Sun in a counter-clockwise (or direct) direction....more

## How do Astronauts Live in Space?

Almost everyone has a question or two about living in space. What do astronauts do in space? How do they do everyday things like eat, sleep and go to the bathroom? It's important to note that astronauts...more

## How far is the Earth from the Sun, the Moon and all the other planets? How far are all of the planets from the Sun? Do you know of a software that tracks the planets in real-time?

There is a really neat internet program called Solar System Live that shows the position of all of the planets and the Sun for any given day. If you go to that page, you'll see an image similar to the...more

## Is it really true that man never really walked on the Moon?

The picture of the American Flag (the one put there by the Apollo astronauts) is waving (or straight out) in the wind. How could that be possible if there is no atmosphere on the Moon? Was it some sort...more

## How many planets orbit the sun?

I was wondering if there is a new planet? Are there planets (a tenth planet?) after Pluto belonging to our solar system? What are the names of the new planets discovered in the solar system? Are there...more

## According to Stephen Hawking, any object with an energy which equals Plank's energy has to become a black hole.

If that is so, the energy released during the Big Bang must have created many such black holes. Therefore most of the Energy of the Big bang must have disappeared in that form. Then how did the Universe...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information.