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#123 - David Baker - Baryonic Acoustic Oscillations

Orbiting Earth in the spaceship, I saw how beautiful our planet is. People, let us preserve and increase this beauty, not destroy it!

Yuri Gagarin

"Can it be that you have come from outer space?"

"As a matter of fact, I have!"

Remember Saturday is Birthday of Yuri Gagarin, Russian colonel, pilot, and astronaut (b 1934 - d. 1968)

Quick Space News

The Beresheet lander took an image showing part of the spacecraft and, in the distance, Earth

OK Go is helping with the "Art in Space" contest. Students ages 11-18 can submit ideas for art they'd like to perform in weightlessness. Winners will get their art flown on a future New Shepard mission.

Mars InSight Lander's 'Mole' Pauses Digging

"The mole is healthy and performed a round of hammering on the weekend. It has, thus far, continued to work against some resistance without clear evidence for progress. The team has therefore decided to pause the hammering for about two weeks to allow the situation to be analyzed more closely and jointly come up with strategies for overcoming the obstacle"

The first all-woman spacewalk later this month.

NASA astronauts Anne McClain and Christina Koch are scheduled to carry out the spacewalk March 29,

Japanese scientists released video of a successful landing on asteroid Ryugu by Hayabusa2 spacecraft.

Asteroid 2015 EG flew past Earth on March 4th.

Luckily for us it was a mere 274 thousand miles away.

Getting SPACEX Demo Mission 1 into perspective.

  • SpX-DM1 (SpaceX Demonstration Mission 1) the orbital test SpaceX human rated Dragon 2, which according to Musk is pretty much completely different to Dragon.

  • This first spaceflight was an uncrewed mission.

  • Fueled while the imaginary crew was aboard

  • It launched on March 2, 2019[6][7] at 2:49 AM EST chased down the International Space Station on March 3, a little over 24 hours after the launch.

  • The launch was pretty much the most bring part of the mission, we’ve seen a lot of Falcon 9 Block 5 flights now, and this was not really any different.

  • The docking phase, as well as the return and recovery of Crew Dragon, include many first-time events that cannot be totally modeled on the ground and, thus, are critical to understanding the design and systems ability to support crew flights

  • The really cool bit was the Dragon 2 capability of docking with the ISS with complete automation. Previous Dragon capsules are captured by skilled astronaunts and the Canadarm.

  • During the spacecraft’s approach, in-orbit demonstrations included rendezvous activities from a distance of up to 2.5 miles, known as far field, and activities within one mile, known as near field. As the spacecraft approached the space station, it demonstrated its automated control and maneuvering capabilities by reversing course and backing away from the station before the final docking sequence.

  • After making 18 orbits of Earth the Crew Dragon spacecraft successfully attached to the International Space Station’s Harmony module forward port via “soft capture” at 5:51 a.m. EST on Sunday, March 3. The Crew Dragon used the station’s new international docking adapter for the first time since astronauts Jeff Williams and Kate Rubins installed it August 2016

  • Ironically the original International Docking Adapter (IDA 1) was destroyed on a spaceX dragon CRS-7 launch failure.

  • Vital life Support systems were monitored for the entire period

  • Instead of carrying astronauts to the ISS, this flight has a test dummy named Ripley after Sigourney Weaver's character in Alien outfitted with sensors to provide data on potential effects on humans traveling in Crew Dragon.. The capsule is also carrying more than 400 pounds of supplies and equipment

  • This according to Musk has been a very collabrative effort with NASA with whome he says, SPACEX wouldn’t be able to exist without the incredible work that was done before SpaceX even started and without the support after SpaceX did start.. He was very emotional and spaced out at conference after Launch describing it as very stressful.

  • Musk made effort to point out the improvement in safety over other systems by having an intergrated launch escape, instead of the a “tractor” in the form of four side-mounted thruster pods with two SuperDraco engines each

  • The ISS crew reported detected elevated levels of isopropyl alcohol in the station after the Crew Dragon spacecraft docked there Sunday. A Russian industry source said the crew detected a "high concentration" of the chemical in the station's air after hatches between the spacecraft and station were opened, suggesting it was contamination from the spacecraft. The crew also noticed an "unusual smell" from the spacecraft, according that source. NASA has not reported any issues with the station or the spacecraft since the docking.

  • The initial idea was to have the crew demo flights in 2015!!, DM1 was the slated to happen in december 2016, but here we are in March 2019. What do we have a Capsule based launch vehicle, and although It brings the US one-step closer to the return of human launches to the space station from the United States for the first time since 2011 – the last space shuttle mission.

  • We just don’t think its as exciting or historical as say the Change’4 or Beresheet. Afterall it only has one more seat compared to Soyuz as far as NASA are concerned, they will not use the 7 seats available. It may work out a lot cheaper than Soyuz, and it’s definitely preferable to give SpaceX the money than Russia at the moment. But the trunk is smaller than the Shuttle, and the Shuttle also had a lot of reusability. The Shuttle could actually carry about 3 dragons up to space. The price per seat $58million, You could say that Shuttle was about $43million a seat if it was taking a large payload as well. And the dragon lands at sea!

  • Additional spacecraft mission objectives include a safe departure from the station, followed by a deorbit burn and parachute deployment to slow the spacecraft before splashdown in the Atlantic Ocean, off the Florida Space Coast. SpaceX’s recovery ship, Go Searcher, will retrieve Crew Dragon and transport it back to port. Teams will be closely monitoring the parachute system and entry control system operation, which have been changed from cargo Dragons to provide higher reliability for crew flights.

  • Cargo Dragon 2 which was chosen alongside dreamchaser in CRS2 back in 2016, will fly next year.

Space Word of the week


An equal-area, pseudocylindrical map projection generally used for global maps of the world or night sky. It is also known as the Babinet projection or elliptical projection.

The Mollweide projection trades accuracy of angle and shape for accuracy of proportions in area, and as such is used where that property is needed, such as maps depicting global distributions. It’s great for weather systems, starmaps and the CMB

Baryonic Acoustic Oscillations

Fossilised into the night sky by way of the distribution of galaxies.

Since the Big Bang, 13.7 billion years ago, the universe has passed through many different phases, it arguably saw more activity and change during the first second than in all the billions of years since. The observable universe was approximately 10 light-years in radius after a second

After the first 1 millionth of a second and for the first 379,000 years the universe was a plasma of electrons, protons, neutrons and other baryonic matter, dark matter and Photons, Why a plasma?, it was just WAY too hot for any atoms to form.

In this intense glowing opaque soup the photons couldn’t escape as light, as they would bump into electrons and basically just couldn’t go in a straight line, there essentially was no light.

But as this bubble of plasma, ie the universe, expanded it was also cooling and at 379,000 years in we have an event called recombination, as the plasma reaches 3000K the electrons are captured by the protons and we have the first Atoms in the universe: Hydrogen. At this point we have photons able to travel in straight lines and Light is born!!! Observable Universe had a radius of approximately 42 million light-years at the time of recombination.

This event is just a miracle as it gives us a window into all that happened before. There is a spherical shell ever expanding away from us from this period, and is called the surface of last scattering, where the recombination happened and light first entered the universe. As the universe has expanded the light waves have been stretched (red shifted) to the microwave spectrum. The map of this surface is the famous CMB, cosmic Microwave background and is a Mollweide map to show equal area as that is the important factor astronomers wished to preserve. The spectrum is so precisely that of black body radiation, the observed and theoretical curve are impossible to tell apart. The universe has expanded so far now that the temperature has dropped to 2.72 K.

So what about these acoustic oscillations, well these are vital in telling what was happening to this plasma before the recombination event, as we can’t see beyond this event, but we can see the fossils of these vibrations. In fact we can actually see to a point when the Universe was subatomic in size, cosmologists believe that random quantum fluctuations in this tiny universe are expanded during inflation, which did a good job at smoothing out the universe, but still would have left density fluctuations.

These tiny density fluctuations would have pulled the dark matter towards them gravitation-ally, but as a result trapped photons would start exerting a radiation pressure outwards carrying the baryonic matter with it and started a true sound wave, a pressure fluctuation propagating through the plasma at the speed of sound, which in the plasma medium is a whopping ½ the speed of light. These massive sound bubbles expanded for the duration of epoque before recombination, but at the point of recombination they were essentially frozen, as the speed of propagation dropped from ½ the speed of light to a few 100m per second. The radius of the shell of this acoustic bubble became fixed with the expansion of the universe, and is called the sound horizon and was about 500,000 light years. Due to the expansion of the Universe these acoustic bubbles will now be 500 million light years across. But can we see them ...hell yes!!! If you tally up the distances between all the galaxies from one another you get a lovely smooth graph except there is a bump at this magical 500 million light years, the distance form the center of the acoustic oscillation where all the dark matter gathered, and therefore where loads of galaxies formed and the out edge of the sound horizon where a density area would also form galaxies.

Spotted in 2005 by the Sloan digital sky survey in the north and the 2df in the south sky, and is exactly the number expected and is a stunning experimental proof of dark energy

By looking at the patterns in the cosmic background radiation, we know how big the rings were when they formed and how big they are now, and this gives us the expansion rate of the universe and it agrees with the standard candle measurement, at least in that the universe expansion is accelerating, a stunning proof of dark energy and how it follows Einsteins cosmological constant.

Hey but that’s not ALL, thinking about the Acoustic oscillations in more detail, and the fluctuations in the heat (anisotropy) we can see in the CMB from satellites like ESA’s Planck (see episode 70), WMAP and COBE we can go even further, The power spectrum of these heat differences can be mapped out as a smooth graph that has several peaks, the first peak tell us about the curvature of the universe (it appears flat), the second peak tells us about the density of the baryonic matter, the third peak the dark matter density.

The fossil of the Acoustic vibrations of the early universe are revealing the nature of the Cosmos in just unbelievable details ..we live in amazing times.

Space Fact

The Milky way mass 3,000,000,000,000,000,000,000,000,000,000,000,000,000 Kilograms or 3 Duodecillion Kg

In a striking example of multi-mission astronomy, measurements from the NASA/ESA Hubble Space Telescope and the ESA Gaia mission have been combined to improve the estimate of the mass of our home galaxy the Milky Way: 1.5 trillion solar masses within a radius of 129 000 light-years from the galactic centre.

despite decades of intense effort, even the best available estimates of the Milky Way's mass disagree wildly. Previous estimates of the mass of the Milky way ranged from 500 billion to 3 trillion times the mass of the Sun.

This huge uncertainty arose primarily from the different methods used for measuring the distribution of dark matter – which makes up about 90% of the mass of the galaxy.

"We were lucky to have such a great combination of data," explained Roeland P. van der Marel (Space Telescope Science Institute, USA). "By combining Gaia's measurements of 34 globular clusters with measurements of 12 more distant clusters from Hubble, we could pin down the Milky Way's mass in a way that would be impossible without these two space telescopes."