Early life likely began a. in the atmosphere b. in the ocean c. on the Earth’s surface
All kinds of life are made of a. very similar chemicals b. very different chemicals c. an equal mix of similar and different chemicals
Life probably began when molecules bonded to form a. RNA b. DNA c. mRNA
Discussion/essay questions
The origin of life on Earth is one of humanity’s most important and controversial questions. Why do you think this is? Do you think religion and science have the same purpose?
Transcript
Abiogenesis is the process that causes non-living materials to become living things. Abiogenesis is one of the greatest mysteries in science. Early life likely began in a “chemical soup” in the ocean. Scientists have observed that all kinds of life are made of very similar chemicals. People, plants, animals, and bacteria all share a common ancestor, which lived about 4.2 billion years ago. Most scientists agree that life probably began when molecules in the chemical soup bonded to create RNA. RNA can cause the chemical reactions that made early life possible, and it can also store information. This allows it to replicate itself. Some scientists have tried to begin the process of RNA bonding in labs. However, no one has ever observed abiogenesis. Because all life is made of the same chemicals, many scientists believe that abiogenesis has only happened once on Earth.
The biosphere is a. the surface of the Earth, where there is plenty of light and oxygen b. the areas of the Earth where most plants and animals live c. all of the areas on Earth that can sustain life
Microbes that can live in environments without much water, sunlight, or oxygen are called a. eukaryotes b. extremophiles c. eubacteria
The “shadow biosphere” hypothesis suggests that a. life on other planets is probably very similar to life on Earth b. new types of bacteria are evolving very quickly underground c. Earth may contain microbes that have very different chemical structures from us
Discussion/essay questions
Do you believe in life on other planets? Why or why not? Why do you think we haven’t found any?
Transcript
The biosphere is all of the areas on Earth that can sustain life. Most complex plants and animals need lots of water, oxygen, and sunlight to survive. When scientists look for life on other planets, they seek places that have the potential to provide these things. On Earth, however, certain microbes thrive in environments that are low in these essential ingredients. These microbes are called extremophiles. They live in volcanoes, deserts, and Antarctic ice. Some extremophiles survive because they can use unusual chemicals to sustain themselves. It is possible that Earth contains microbes with chemical structures that are very different from our own. This hypothesis is called the “shadow biosphere.” A shadow biosphere would be made up of life that is chemically unrelated to life as we know it. If this type of life exists, there may be more habitable planets than we think.
The escape velocity is a. the maximum mass of an object travelling into space b. the minimum mass of an object to be a strong source of gravity c. the minimum constant speed of an object travelling into space
The escape velocity of Earth is about a. 9.8 km/s b. 11.2 km/s c. 40,000 km/s
It would be easiest to launch an object from a. Earth b. the Moon c. a black hole
Discussion/essay questions
Reaching outer space was an important achievement in human history. What kinds of space exploration do you think will be possible in the future?
Transcript
Every source of gravity in the universe has an escape velocity. This is the minimum constant speed that an object has to travel to fully escape from a planet or star and enter outer space. For an object of any mass to be launched into space from Earth, it must be travelling at about 11.2 km/s, or 40,000 km/h. To determine escape velocity, scientists need to know the mass and radius of the source of gravity. Escape velocity increases for planets and stars with more mass. It would be easier to launch something from the Moon than from Earth. For a black hole, which has infinite density, the escape velocity is greater than the speed of light. This is why nothing can possibly escape from its gravity.
The universe is about a. 4.5 billion years old b. 13 billion years old c. 50 billion years old
Fermi thought that if older civilizations existed, a. they should have contacted us already b. they wouldn’t be friendly to us c. they would have destroyed each other
The Great Filter is a. a hypothetical barrier that stops life from developing b. a hypothetical type of technology for interstellar travel c. a hypothetical civilization that has the power to contact other civilizations
Discussion/essay questions
Do you believe in life on other planets? If so, why do you think they haven’t contacted us? If not, what makes you think we’re alone?
Scientists who believe in the Great Filter are not sure if we are past it. What could stop life on Earth from developing further?
Transcript
The Fermi paradox is based on a question asked by a scientist named Enrico Fermi: if the universe is so large, why haven’t we found intelligent life yet? Although it is a very simple question, it has confused scientists for decades. The universe has existed for over 13 billion years, but our planet is only about 4.5 billion years old. Fermi believed that if human life could develop so quickly, there surely had to be older, more advanced civilizations out there. These civilizations likely would be capable of interstellar travel. If this is true, then aliens should have contacted us already. Many people have proposed explanations since Fermi first asked the question in 1950. One possibility is something called a Great Filter, which is a hypothetical barrier that stops most types of life from developing past a certain point.
Do you believe in life on other planets? Why or why not?
Do you think that aliens could be discovered in our lifetime?
Transcript
An exoplanet is a planet outside of our solar system. Most exoplanets orbit different stars in the galaxy. However, astronomers have observed some planets that are independent of any star system. The first two exoplanets were discovered in 1992. Since then, scientists have been searching for exoplanets that are similar to Earth. This might lead to the discovery of alien life. However, Earth-like planets are difficult to find, because the resources necessary for life only exist under very specific conditions. Our planet happens to be in the solar system’s habitable zone, where the temperature allows water to exist in liquid form. There are over 1,700 known exoplanets, and only 16 of them are potentially habitable.
