Something else to consider is the curvature of space. Taking together all the stuff we know about the universe, astronomers at the University of Oxford calculated that the universe might be as much as seven trillion miles wide, 250 times the part of the universe that we can see.īut what if dark energy doesn’t exert its influence uniformly across the universe? Then, all bets are off about the universe’s size. A mysterious force astronomers call dark energy appears to be responsible for the increase. However, the expansion Universe seems to be getting faster than expected. If that’s the case, the Universe might be smaller than 93 billion light-years wide. The gravity of all the galaxies interacting should drag down the speed. You’d expect that the expansion of the universe is slowing down after all this time. If it got bigger at a constant rate after cosmic inflation, the universe would have a radius of over 46 billion light-years and a diameter of nearly 93 billion light-years. During the 13.8 billion years since the Big Bang, the universe has continued to get bigger at nearly the speed of light.įurthermore, during the first billionth of a second after the Big Bang, the universe expanded much faster than the speed of light, a period called cosmic inflation. And we are at the center of the ball.īut that’s not the answer, I am sorry to say. It began with a rapid expansion that astronomers call the Big Bang.Ĭonsequently, from our perspective, the universe looks like a ball of galaxies and microwave radiation with a radius of 13.8 billion light-years or a diameter of 27.6 billion light-years. Astronomers estimate that the universe is 13.8 billion years old. The farthest light we can see is the Cosmic Microwave Background radiation, which happened 385,000 years after the Universe began.īefore that, there was no light to see. The light from them takes as long as 13.2 billion years to get to the Earth. The farthest galaxies from us are also the oldest. Using space-based telescopes, astronomers have observed light from extremely distant galaxies. Trillions of galaxies make up the Universe. It took over two million years for the dim light of that galaxy to get here. It’s much farther away than the stars in our galaxy. The closest major galaxy to ours is the Andromeda Galaxy. That’s big, but it’s nothing compared to the distances between galaxies. If you turned on a flashlight at one end of the Milky Way, the light would take about 100,000 years to get to the other end, making our galaxy about 100,000 light-years across. The Milky Way is a pinwheel-shaped collection of stars, dust, and hydrogen gas. The sun and Alpha Centauri are two of about 300 billion stars that make up our home galaxy, the Milky Way. The nearest star to the sun is Alpha Centauri, over four years away by light beam. Neptune, the farthest planet from the sun, is more than four light-hours away from us.īut the stars are much farther apart than the planets are from our star, the sun.
The planets in our solar system that are farthest from us are in orbits that are hours away by light beam. That makes Earth over eight “light minutes” from the sun. The light from the sun takes over eight minutes to get to our eyes. Earth is the third planet from the uun of the eight major planets revolving around it. Let’s start close to the Earth and work our way out. A light-year is the distance it takes light to travel in one year - about 6 trillion miles. So astronomers use measures like the “light-year” to talk about the distance from one astronomical object to another. The universe is so big that our usual distance measures are too small to make much sense. Old Captain Astro’s mind exists in a perpetual state of cosmic bogglement. It’s so big that it’s hard for mere mortals like us to comprehend how big.Īren’t you going to answer any of these questions? At a time when people are saying that youngsters like yourself aren’t interested in science, it’s a pleasure to see that you know so much about astronomy. What are the spectral characteristics of Seyfert galaxies? Tom was up observing all last night, so he’s asked his good buddy, the Amazing Captain Astro, to answer some of the many questions about astronomy that have been pouring in.
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