Why have we never actually seen our galaxy?The reason is simple: In order to get that long view of the Milky Way's arms, we'd need a spacecraft to be outside the galaxy. We've never even sent one outside our solar system (though we are very close).
How many galaxies have humans seen?One such estimate says that there are between 100 and 200 billion galaxies in the observable universe. Other astronomers have tried to estimate the number of 'missed' galaxies in previous studies and come up with a total number of 2 trillion galaxies in the universe.
Can we see our own galaxy in the past?While astronomers cannot see actual past incarnations of the Milky Way, Hubble lets them see far distant, fundamentally similar galaxies, representing the Milky Way's appearance at different moments in time. A word about seeing into the past: Light takes time to travel.
How far back in time can we see?We can see light from 13.8 billion years ago, although it is not star light – there were no stars then. The furthest light we can see is the cosmic microwave background (CMB), which is the light left over from the Big Bang, forming at just 380,000 years after our cosmic birth.
The Milky way Galaxy Facts | How do we know our Galaxy is spiral? |
Is looking into space looking back in time?Whenever we observe a distant planet, star or galaxy, we are seeing it as it was hours, centuries or even millennia ago. This is because light travels at a finite speed (the speed of light) and given the large distances in the Universe, we do not see objects as they are now, but as they were when the light was emitted.
What is beyond the universe?The trite answer is that both space and time were created at the big bang about 14 billion years ago, so there is nothing beyond the universe. However, much of the universe exists beyond the observable universe, which is maybe about 90 billion light years across.
How many universes are in space?We currently have no evidence that multiverses exists, and everything we can see suggests there is just one universe — our own.
Why is space infinite?Because space isn't curved they will never meet or drift away from each other. A flat universe could be infinite: imagine a 2D piece of paper that stretches out forever. But it could also be finite: imagine taking a piece of paper, making a cylinder and joining the ends to make a torus (doughnut) shape.
Have any human made objects left our galaxy?Voyager 1 was the first spacecraft to cross the heliosphere, the boundary where the influences outside our solar system are stronger than those from our Sun. Voyager 1 is the first human-made object to venture into interstellar space.
What do scientists think our galaxy really is?They come in a variety of shapes and sizes. The Milky Way is a large barred spiral galaxy. All the stars we see in the night sky are in our own Milky Way Galaxy. Our galaxy is called the Milky Way because it appears as a milky band of light in the sky when you see it in a really dark area.
How many times have we gone around the galaxy?Orbiting the Galaxy
It takes our Sun approximately 225 million years to make the trip around our Galaxy. This is sometimes called our “galactic year”. Since the Sun and the Earth first formed, about 20 galactic years have passed; we have been around the Galaxy 20 times.
Does space ever end?Practically, we cannot even imagine thinking of the end of space. It is a void where the multiverses lie. Our universe alone is expanding in every direction and covering billions of kilometres within seconds. There is infinite space where such universes roam and there is actually no end.
Is space ever truly empty?One is quantum-mechanical in nature. Quantum field theory, the tool we use to study particle physics, says particles flicker in and out of existence, even in a vacuum. In other words, once quantum effects are taken into account, there is no such thing as completely empty space-time.
What's at the end of space?Scientists now consider it unlikely the universe has an end – a region where the galaxies stop or where there would be a barrier of some kind marking the end of space. But nobody knows for sure.
How many dimensions exist?The world as we know it has three dimensions of space—length, width and depth—and one dimension of time. But there's the mind-bending possibility that many more dimensions exist out there. According to string theory, one of the leading physics model of the last half century, the universe operates with 10 dimensions.
Is there another Earth in space?Using data from NASA's Transiting Exoplanet Survey Satellite, scientists have identified an Earth-size world, called TOI 700 e, orbiting within the habitable zone of its star – the range of distances where liquid water could occur on a planet's surface. The world is 95% Earth's size and likely rocky.
What created the universe?Our universe began with an explosion of space itself - the Big Bang. Starting from extremely high density and temperature, space expanded, the universe cooled, and the simplest elements formed. Gravity gradually drew matter together to form the first stars and the first galaxies.
Is there an edge to the universe?One thing's for sure: the Universe does not have an edge. There's no physical boundary – no wall, no border, no fence around the edges of the cosmos. This doesn't necessarily mean that the Universe is infinitely large though.
Can we get out of the universe?Thanks to dark energy and the accelerated expansion of the Universe, it's physically impossible to even reach all the way to the edge of today's observable Universe; we can only get a third of the way there at maximum.
Could we ever look into the past?1) We have no way of catching up to light from the past.
It travels faster than we can ever hope to, so we would never be able to set up a mirror in a place that would reflect light from before when we left earth to set up the mirror.