what questions do we still have about the universe?
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What Questions Do We Still Have About the Universe?. By Joe D. The Big bang. Most astronomers believed that the universe was born in a period of extremely fast inflation called the big bang. Before the Big Bang, the universe was just a very densely packed and very hot dot. - PowerPoint PPT PresentationTRANSCRIPT
WHAT QUESTIONS DO WE STILL HAVE ABOUT THE
UNIVERSE?
By Joe D.
THE BIG BANG• Most astronomers believed that the universe was born in a period of extremely fast inflation called the big bang. • Before the Big Bang, the universe was just a very densely packed and very hot dot.
• Scientists is still not sure exactly when exactly did the big bang happen. Some say it happened 13.7 billion years ago, others argue it happened 13.8 billion years ago.
In this section, you’ll learn more about the big bang!
What came after the Big Bang?
• A lot of things happened in just a few fractions of a second after the big bang:
•The pressure was so high that all the forces of nature (gravity, electromagnetic, the strong nuclear force and the weak nuclear force) was unified
Big Bang Planck epoch
Grand unification
epochInflationary epoch
Electroweak epoch
Quark epoch
Hadron epoch
Lepton epoch
Photon epoch
Big bang nucleosynthesis Photon epoch
KA-BOOM!!!!
• During the Grand unification epoch (approximately 10-43 seconds) gravity separated.
• About one picosecond (one trillionth of a second) after the Big Bang, the weak nuclear force separated from the electroweak force resulting in the four separate forces we know today.
•10-35 seconds after the big bang the strong nuclear force separated. •10-36 seconds after
the Big Bang the universe started expanding faster than the speed of light (299 792 458 m/sec.)!
• About one nanosecond (one billionth of a second) after the Big Bang quarks formed, but it’s way too hot for atoms to be created.
• One second after the big bang, the temperature has fallen to 28 billion degrees Celsius.
• After three minutes the temperature became 555 million degrees Celsius, it became cool enough for very light nuclei to form, like hydrogen, helium.
What Evidence do we have to Keep the Theory Alive?
• Scientists got interested in how the universe started just recently.• There are strong evidence saying that the big bang really happened. • Cosmic microwave background (CMB) radiation is one of the most strongest evidence supporting the big bang theory.
• CMB radiation is the energy “echo” left over by the big bang. •CMB radiation originated more than 13.7 billion years
ago, when the universe was only about 380,000 years old.•Another evidence is: the universe is expanding since
the big bang, so it must start with a singularity
What Scientists don’t know about the Big Bang
• The big bang is just a theory, it’s just the most accepted theory of how the universe was created.
• The big bang theory has evidence supporting it but it’s unknown to scientists if the big bang really happened.
• No one knows what happened before the big bang, was it a singularity?
• Some scientists say that before the big bang there were nothing but that scenario violates the first law of thermodynamics (which says you can’t create or destroy matter or energy).
• There are still a lot of unsolved questions about the big bang.
• In the future, people may create more theories about how the universe got started.
BLACK HOLES• A black hole is matter densely packed into an extremely small dot. • The “dot” is the black hole’s central singularity, and because all matter have gravity (even humans!), the gravity in a black hole is super strong because there’s so much matter in the black hole’s singularity, and of course, it’s squished into an extremely small space. • A black hole’s gravitational force is so strong in the event horizon that even light cannot escape
• If an object is squished to fit into an extremely small space, it can become a black hole, but huge amounts of energy is needed to squish an object into a very dense dot.
• Singularities are regions of infinite density and zero volume
•In this section, you’ll learn about how do they form and see pictures about black holes and many more!
Parts of a black hole
How are black holes born?
• Black holes are born usually from dying stars. Our sun will never become a black hole; although it’s a star, not all star become black holes. • Some researchers say that a star must be at least 3 to 10 times the mass of the sun to become black holes. • Others argue that it takes at least 25 solar masses!
• When massive stars run out of hydrogen, they start to fuse helium then carbon, then oxygen and so on.
Did you know that?Actually, anything can be a black hole! Unfortunately, your book or your Lego set cannot become a black hole (if it does, it’s going to evaporate in less than a nanosecond anyways) because vast amounts of energy is needed to compress your Lego set into 0.1 billionth of an meter (Yep, you have to compress it to about 0.1 billionth of a meter to create a black hole!).
A bright hypernova
• Very massive stars can continue until iron but after iron they explode as a supernova then either become a neutron star or a black hole.• Black-hole-making stars sometimes die in a very bright and high energy explosion called a hypernova.• Merging neutron stars can become black holes as well.
Did you ever wonder what will you see when you fall Into a black hole?
• Let’s imagine you fell leg-first into a black hole.
• Before you fall in, you’ll see some stars around you but their light is distorted by the black hole, so you will see lots of images of the same star in different parts of the sky.• You’ll also see a circle of perfect darkness in front of you. • Release! You will see that the black spot a.k.a. the event horizon is coming toward you very quickly……• You can still see the sky but it gets more and more distorted and eventually the sky is just a thin band.
What will you see?
What will you feel?• You’ll feel gravity pulling stronger at your legs than you head. • If you fall into a stellar-mass black hole you will be broken apart to the individual atom before you even reach the event horizon!
• If you fall into a supermassive one, you can survive even after the event horizon!
Types of Black HolesMicro Black Holes (also called mini or
quantum mechanical black holes)• Miniature black holes is a hypothetical type of black hole, micro black holes are less than one solar mass.• Although no one ever saw one, scientists think they exist • Scientists think there are two ways to create these black holes.1. Shortly after the big bang,
denser clumps of matter may form black holes of various sizes.
2. People in the future may create these micro black holes in particle accelerators.
Stellar-mass Black Holes
Stellar-mass black holes are black holes that born from massive stars dying. These black holes are usually around 10 solar masses. Usually, stellar-mass black holes have companion stars or matter orbiting them like the one shown in the picture below.4U 1630-47 star system
Intermediate-mass Black Holes• Intermediate-mass black holes are also a hypothetical type of black hole.• These black holes range from 100 to one million solar masses. • Their mass is more than a stellar-mass black hole and slightly less than a supermassive black hole. • No one ever detected an intermediate-mass black hole but more evidence is building up.
Supermassive Black Holes
• Supermassive black holes are the biggest type of black holes ever found.
• Galaxies almost always have supermassive black holes at their centers.• Supermassive black holes can range from hundreds of thousands to billions of solar masses.
Charged Black Holes (Reissner-Nordstrøm black holes)
• Charged black holes have a electrical charge.
• Whoa…two event horizons!
• The singularity of a charged black hole is the same as that of a static black hole (a black hole with no charge and no rotation) except for two difference:
1. The singularity is allowed to exist without the event horizons. No “naked” singularities are observed yet.
2. The other difference is that when you travel pass a static black hole’s event horizon: end of your life, but when you survive the two event horizon of a charged black hole, theoretically you could just leave!
http://vimeo.com/8724840
Journey into a charged black hole (video)
Kerr Black Holes• Some black holes rotate!
• Rotating black holes are called Kerr black holes and Kerr-Newman black holes.
• Kerr-Newman black holes is a charged black hole and a rotating black hole.
• These black holes are actually the most common type of black hole!
• The space around the black hole gets dragged around, creating a giant cosmic whirlpool.
• Stars rotate, so the rotation is transferred to the black hole
• Rotating black holes have two event horizons and two photon spheres. • The corotating photon sphere is faster than the conterrotating photon
sphere.
• The photon sphere(s) are where photons or light can hold unstable orbits around the black hole.
What We Don’t Know about Black Holes
• No one knows what happens to space and time at the singularity of a black hole
• What is on the other side of a black hole?
• Scientists are wondering: how could supermassive black holes get so big?
WORMHOLES• You’ve probably heard the name in Star-Trek movies, but scientists think wormholes aren’t sci-fi anymore.
• A wormhole is also called a Einstein-Rosen Bridge.• In this section, you’ll learn about wormholes!
What is a Wormhole?• A wormhole is a
“shortcut” connecting two distant points in space-time
• A wormhole has two “mouths” and a “throat” connecting them.
• However, some wormholes might be connecting a black hole and a white hole.
Wormhole mouth Throat
• With wormholes, we might be able to travel to a distant galaxy in a short period of time.
• Unfortunately, wormholes are not proven to exist yet.
• Microscopic wormholes may be popping in and out of existence in quantum foam.
• Microscopic wormholes might be traversable but they’re way too small for humans or any spaceship to go though them.
• These incredibly small wormholes are just a billionth trillionth trillionth of a cetimetre across.
Types of wormholesMicroscopic Wormholes?
A interesting video about microscopic wormholes.
http://youtu.be/SLUzJeto0Wo
• You can’t travel though a Schwarzschild wormhole.
• The wormhole will collapse before you’re on the other side.
• Einstein’s theory of general relativity mathematically predicts these very unstable and dynamic wormholes.
Schwarzschild Wormholes
Traversable Wormholes
• Some scientists say Schwarzschild wormholes can be held open by exotic matter (negative matter).
• Negative matter has
negative energy.
• Futuristic technology can probably even create traversable wormholes!
Time Travel• Could wormholes be the
answer to traveling though the fourth dimension?
• Some scientists believe that wormholes may be the answer to time travel.
• They say: if you spin one of the wormhole’s mouths in a specific way, it will allow time travel.
• However, others argue that such use is not possible.
Other Universes?
• There might be other universes waiting for us to explore.
• There might be aliens or other interesting stuff in the “other” universe.
• These universes may be accessible using wormholes!
What Questions do We Still have about Wormholes
• There are no observational evidence that they exist, but that’s not proof that they don’t exist
• We still don’t know if wormholes are even real yet!
• A major problem about traversable wormholes is: how could we possibly create so much exotic matter?
Thanks for listening to my presentation! I hope you’re going to learn more about space and its wonders.