Is There Life Outside Earth? Will the Human Race Ever Be Able to Live On Other Planets?
Everyone knows that the Earth is the only place in the universe where life exists. Right? Not exactly. While it’s true that the Earth is the only planet that we know of with life, there are some very good reasons to think that it might not be the only planet with an abundance of life – and even more reason to think that there must be other planets out there somewhere with conditions capable of supporting human life. In fact, science has been exploring this subject for centuries and has made phenomenal leaps in our understanding of alien life and its possibility in our galaxy just within the last few decades. If you find yourself saying “Yeah, right” because you assume it’s all just science fiction, read on – we have some convincing arguments for you!
What’s the Difference Between Living and Non-Living Things?
When you look at a plant or an animal, it’s easy to think that you’re seeing a living thing – plants grow, animals move, both consume nutrients and reproduce. But if you look carefully at a sample that is believed to be lifeless, like a piece of stone, it’s harder to see how it could be living. But a living thing is actually much more than these visible actions. Living things are made up of cells. Each cell has a nucleus that contains DNA – genetic information that directs the cell to perform the functions necessary for the plant or animal to survive. All living things use the same basic genetic code to direct their activities. The DNA directs the cell to make proteins, which determine the cell’s function and structure. In contrast, non-living things are not made of cells. Non-living things are molecules that are chemically bound together. In general, non-living things are not able to grow or reproduce.
How Do We Know If There Is Life Outside Earth?
Although we have evidence that the Earth is not the only place in the universe with conditions that are necessary for life, it’s important to understand why we can’t just go outside and look for life. The most obvious reason is that these other planets are too far away to reach even with our fastest rockets – the nearest star outside our solar system is about four light years away! There are, however, other reasons for not being able to go out and inspect other planets for signs of life. Since it is very difficult to get out there to take samples and bring them back, we have to rely on systems that can be used here on Earth.
For instance, if there really is life on other planets, we would expect to see certain signs of its existence. As one example, we know that plants on Earth produce oxygen as a by-product of photosynthesis, so if we found oxygen in the atmosphere of another planet, that could be a sign that photosynthesis was happening there too.
Why Might There Be Other Planets With Life?
The Earth is a very special planet. It is located in the Goldilocks zone of our solar system, which is neither too hot nor too cold to support life. and the chemical elements that are necessary for life are all present in the sun and in the Earth’s crust. Life first appeared on Earth very early in the planet’s history, only a few hundred million years after it formed. This suggests that conditions were right for life very early on.
There are lots of good reasons to think that there might be other planets in the universe with life. For one thing, the conditions needed for life to exist are very common in the universe. You only need some hydrogen, carbon, nitrogen, and oxygen as building blocks, and you can make anything you find on Earth or in your body (including blood, skin, bones, and muscles). Hydrogen, nitrogen, and carbon are the three most common elements in the observable universe. Oxygen is only a bit less common. It’s also possible that there is plenty of water throughout the universe. The sun and other stars might have the ability to make water molecules, which would then get made into ice and sent out into space where it could eventually be picked up by other planets. There’s also the idea that a planet might have the ability to make life out of non-living building blocks.
There are many reasons to think that there might be other planets with life. Astronomers have discovered that there are billions and billions of planets outside our own solar system – and some of these are in just the right place to support life. So far, scientists have discovered rocky planets, gas giants, hot planets, cold planets, and even planets that could potentially be habitable. It’s possible, therefore, that other planets have the right conditions to support life, or even that some of them already do! It’s important to emphasize that we don’t know this for sure, yet, but it’s certainly within the realm of possibility. We do know, however, that there are billions of other planets in our galaxy that could sustain life – and billions of galaxies in the universe! This, coupled with our growing understanding of the physics of other planets and solar systems, makes it seem very possible that other planets have life.
Why Might There Only Be Microbes Outside Earth?
The absence of intelligent life, or even simple multicellular organisms, outside Earth could be due to a number of factors.
- The first organisms to develop may have been very primitive microbes. These organisms are single-celled and, as far as we know, this is the simplest form of life. So the first life-forms could have been microbes.
- Microbes could be ubiquitous throughout the universe and Earth’s oceans may be unique in having higher life-forms.
- Life may have evolved earlier on other planets but been extinguished by subsequent asteroid or comet impacts.
There are several other reasons why we should expect to find only microbes outside Earth. First, microbes can easily survive the journey through space, whereas larger organisms like humans would be almost impossible to transport from one planet to another. Second, microbes reproduce quickly and in large numbers. They would be able to survive outside their home planet (if their home planet is one that can support life) and reproduce quickly enough to populate a new planet. Third, microbes can live off of very small amounts of energy – much smaller than organisms like humans require. Therefore, they can survive on planets that have less light, and heat, and more radioactive energy than Earth.
When people think of the possibility of life outside Earth, they often just think in terms of the other planets in our solar system. But there are billions of stars in our galaxy alone, most of which are billions of years older than our sun, so we might expect many of them to have planets that have had longer to evolve life. And indeed, scientists have found plenty of evidence of life on these other stars. There are many good reasons for thinking that there might be life outside Earth. In fact, the only thing that we know for sure about the only place in the universe where we know there is life is that life there is incredibly fragile. If we don’t take care of our planet and reduce human-caused climate change, we may soon find out just how fragile life on Earth really is.