PBS_SpaceTime

Groundbreaking Explanation About How A Circle Can Be A Straight Line8m17s

Groundbreaking Explanation About How A Circle Can Be A Straight Line

General Relativity! Spacetime! And... curved lines? On this week's episode of Spacetime, Gabe talks about what it actually means for a line to be straight so we can better understand what we mean by the idea of "Curved Spacetime". To make it easer he will divide this ground work at three parts: Part one: Geometry, part two: Spacetime, part three: Spacetime + curvature. This is part one of our series on General relativity, so be sure to check it out! Part one is about straight lines and curved spaced, no physics. Gabe gives great explanation about how a curve can be “straight” if tangent vectors stay tangent when parallel- transported along with that curve. Simple, isn’t it? This is great example with an ant confined to the surface of an ordinary sphere with no concept of or an access to the direction off the surface. From the ant’s two dimensional confined prospective, curve one between A and B is straight. The vector tangent to curve one at point A remains tangent all along curve one as we parallel transport it to point B. Once the ant does that over lots of curves joining A and B it finds that the tangent vector will remain tangent only. That segment is called a geodesic and piecewise it’s straight. Topology is global, but geometry and curvature are local. Now what we have learned from Gabe is that in a three dimensional space you can test curvature just by moving a vector parallel to itself around a circle. If you end up with the same vector you started with space is flat, if not, it’s curved.

Here Are 5 Ways To Prevent A Killer Asteroid From Colliding With The Earth8m32s

Here Are 5 Ways To Prevent A Killer Asteroid From Colliding With The Earth

When it comes to dangerous asteroids striking Earth, it's not a matter of if, it's a matter of when. We have begun to track projectiles large enough to destroy our planet, and we are in the clear for the foreseeable future. However, there are countless asteroids large enough to take out an entire city that we cannot see. If you’ve ever watched the movie Armageddon, you know what we are talking about. There is a high probability that sometime in the future we would have to resort to those kinds of actions to save our planet. There is a reason to believe that it hasn’t been the first time an asteroid of large proportions changed the course of history when it fell on the Earth and wreaked havoc on it. The dinosaurs as species were wiped of the face of the Earth by an asteroid that hit the coast of the Yucatan peninsula, triggering a series of changes in the Earth’s climate and biodiversity. The first thing to do when under the threat of an asteroid hitting our only home is trying to locate it sooner rather than later. Efforts have been made to scan as much of the dark sky for flying rocks that are bigger than 500m, so that we are aware of their approach, but it’s still unclear as to where those smaller than 500m are. They are just like a grain of sand in the vastness of space. Other ways of dealing with them include finding a way to change their trajectory, whether by kinetic or gravitational force.

Guide-Through To How To Build A Black Hole10m59s

Guide-Through To How To Build A Black Hole

Earth mysteries are a wide range of spiritual, quasi-religious and pseudo-scientific ideas focusing on cultural and religious beliefs about the Earth, generally with regard to particular geographical locations of historical significance. Believers in Earth mysteries generally consider certain locations to be "sacred", or that certain spiritual "energies" may be active at those locations. The term "alternative archaeology" has also been used to describe the study of Earth mystery beliefs. A black hole is a region of space-time exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it. The theory of general relativity predicts that a sufficiently compact mass can deform space-time to form a black hole. The boundary of the region from which no escape is possible is called the event horizon. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed. In many ways a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved space-time predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for black holes of stellar mass, making it essentially impossible to observe. Black holes have mystified physicists for decades, but with the help of quantum mechanics, we are beginning to make serious progress in understanding these strange objects. This week on Space Time, Matt dives deeper into the physical process of creating a black hole, and what that can tell us about how black holes behave. Take a look as this video is sure to broaden your horizons!

Intriguing Theory About Alien Life And Earth-Like Planets 10m34s

Intriguing Theory About Alien Life And Earth-Like Planets

With millions of Earth-like planets around sun-like stars in our galaxy alone, why don't we see intelligent alien life? Or any other life for that matter? It gets especially weird when you factor in new scientific revelations that life on Earth occurred crazy fast! So if you want to help us theorize on the real reasons we haven't found alien life, you should check this video of Space Time! Why don’t we see alien civilization? The resolution for it has to be that there is some sort of great filter that either makes intelligent life extremely rare in the first place or that wipes out, essentially, all advanced civilization before they get to the galactic empire stage, whether by a nuclear war, environmental catastrophe, accidentally making a black hole that swallows the planet, et etcetera. But some people believe in that and some people just don’t buy that theory. The other logical explanation is that we know of exactly one instance intelligent life happening, the case of the earth. Multicellular life evolved independently dozen of times. It just took a really long time for those single cells to become complex enough to form large collaborative structure capable of collective reproduction, I.e plants, animals, species capable of making the Kerbal Space Program. So what is the great filter? Maybe it’s just time. If life is common then of the billions of Earth-like planets in the galaxy, only a tiny fraction needed to have a small head start on us in order to have produced the Federation of Planets and Stargates and stuff by now. Well, that explains a lot!

Strange Stars9m58s

Strange Stars

What happens when matter can’t get any denser yet somehow does? The answer - it becomes strange. Strange Stars may be the most massive stellar remnant that is just shy of forming a black hole. And they could be even cooler than black holes.

S3 Ep16: White Holes12m25s

S3 Ep16: White Holes

Lurking in the depths of the mathematics of Einstein’s general relativity is an object even stranger than the mysterious black hole. In fact it’s the black hole’s mirror twin, the white hole. Some even think that these could be the origin of our universe.

What Happens At The Edge Of The Universe?7m44s

What Happens At The Edge Of The Universe?

Lots of people believe the Universe is infinite, but there's a good possibility that might not be the case. Which means that there would be an actual edge of the Universe. What happens at that edge? Is there a restaurant?

S3 Ep18: The Future of Space Telescopes10m34s

S3 Ep18: The Future of Space Telescopes

The Kepler mission has determined that terrestrial planets are extremely common, and may orbit most stars in the Milky Way. But these planets are difficult to directly image because they’re dense and small. Our Sun is about ten billion times brighter than Earth. Train a distant telescope on us, and it will be overwhelmed by the Sun’s rays. So how can we find terrestrial planets around stars light

S3 Ep5: Supervoids vs Colliding Universes!10m41s

S3 Ep5: Supervoids vs Colliding Universes!

If you study a map of the Cosmic Microwave Background, or CMB, you may notice a large, deep blue splotch on the lower right. This area, creatively named the Cold Spot. Is this feature a statistical fluke, the signature of vast supervoids, or even the imprint of another universe?

S2: Is Quantum Tunneling Faster than Light?9m53s

S2: Is Quantum Tunneling Faster than Light?

Where are you right now? Until you interact with another particle you could be any number of places within a wave of probabilities. Matt dives into these counter-intuitive ideas and explains the bizarre phenomenon known as quantum tunneling in this episode of Space Time.

S3 Ep19: Are the Fundamental Constants Changing?11m12s

S3 Ep19: Are the Fundamental Constants Changing?

The laws of physics are the same everywhere in the universe. At least we astrophysicists hope so. After all, it’s hard to unravel the complexities of distant parts of the universe if we don’t know the basic rules. But what if this is wrong? There is a hint of evidence that the fundamental constants that govern our universe may evolve over time, and even from one location to another.