Everyone knows the leap day. Every four years (except century years not divisible by 100), an extra day is added to the year in February to keep the calendar in synch with the seasons.
However, there is also a leap second. This is used every couple of years to keep the Coordinated Universal Time close to the mean solar time. The reason why it is needed is that the Earth's rotation is slowing down, but not by a lot.
The second is added just before midnight on either June 30th or December 31st. The time would go from 23:59:59 to 23:59:60 to 00:00:00. The last time a leap second was added to the UTC was last June 30th.
30 June 2016
28 June 2016
Negative Energy
Energy is what is called a scalar in physics. A scalar is a measurement that has a magnitude, but not a direction. Distance and time are other examples of a scalar. Vectors are measurements that have both magnitude and direction. Acceleration, force, and velocity are all examples of vectors.
Note: velocity and speed are not interchangeable in physics. Speed is a scalar, velocity is a vector.
Why is this important to know that energy is a scalar? Scalars are generally always zero or positive. So typically, the energy of a system is always zero or greater. The concept behind negative energy is this:
Suppose you have two objects separated by an infinite distance. The sum total of their energies is zero. Gravitational force then accelerates the two objects together. Therefore, the energy the system is increasing. But a closed system cannot change its energy. Therefore, the difference between the initial condition and the final condition is negative, hence negative energy.
Negative energy is a strange concept to understand and it's only theoretical since the above situation is very simplistic. However, if it does exist and we can harness it, negative energy can lead to humanity colonizing the galaxy (well, at least the local neighborhood). Negative energy can impact warp drives and may be used to stabilize wormholes.
Note: velocity and speed are not interchangeable in physics. Speed is a scalar, velocity is a vector.
Why is this important to know that energy is a scalar? Scalars are generally always zero or positive. So typically, the energy of a system is always zero or greater. The concept behind negative energy is this:
Suppose you have two objects separated by an infinite distance. The sum total of their energies is zero. Gravitational force then accelerates the two objects together. Therefore, the energy the system is increasing. But a closed system cannot change its energy. Therefore, the difference between the initial condition and the final condition is negative, hence negative energy.
Negative energy is a strange concept to understand and it's only theoretical since the above situation is very simplistic. However, if it does exist and we can harness it, negative energy can lead to humanity colonizing the galaxy (well, at least the local neighborhood). Negative energy can impact warp drives and may be used to stabilize wormholes.
27 June 2016
June
June is the sixth month in the Julian and Gregorian calendars. It is believed to be named after Juno, the wife of Jupiter or from the Latin iuniores meaning younger ones.
June is important astronomically as it contains the summer solstice for the Northern Hemisphere and the winter solstice for the Southern Hemisphere.
Important June events:
John Couch Adams, co-discoverer of Neptune, was born on June 5, 1819.
Johannes Muller, inventor of astronomical tables, was born on June 6, 1436.
Pope Gregory XIII was born on June 7, 1502.
Giovanni Cassini was born on June 8, 1625.
Johann G Galle, co-discoverer of Neptune, was born on June 9, 1812.
June is important astronomically as it contains the summer solstice for the Northern Hemisphere and the winter solstice for the Southern Hemisphere.
Important June events:
John Couch Adams, co-discoverer of Neptune, was born on June 5, 1819.
Johannes Muller, inventor of astronomical tables, was born on June 6, 1436.
Pope Gregory XIII was born on June 7, 1502.
Giovanni Cassini was born on June 8, 1625.
Johann G Galle, co-discoverer of Neptune, was born on June 9, 1812.
20 June 2016
Summer Solstice
June 20th, 2016 marks the official beginning of summer in the northern hemisphere. We call this day the summer solstice.
In astronomical terms, the summer solstice for the northern hemisphere occurs when the sun is the farthest north of the equator on the ecliptic. This angular distance is 23.5°, This angle also marks a line of latitude on the Earth called the Tropic of Cancer.
The Tropic of Cancer is so called because the summer solstice used to occur when the Sun was in the constellation Cancer and the latitude lines in the tropical zone. There is also a comparable line of latitude south of the equator called the Antarctic Circle. The latitude is 66.5° South and for anyone living south of this latitude (really, mostly penguins or anyone stationed in Antarctica), the Sun will never rise. Conversely, the Arctic Circle at 66.5° North, the Sun never sets. In fact, from the vernal equinox to the autumnal equinox, the North Pole is in perpetual sunlight, while the South Pole is in perpetual darkness.
The summer solstice marks the day of the year when the northern hemisphere receives the most light. From here on until the winter solstice, the days will only get shorter and the nights longer. In the southern hemisphere, the opposite occurs. Today marks the shortest day of the year and they are in winter time.
In astronomical terms, the summer solstice for the northern hemisphere occurs when the sun is the farthest north of the equator on the ecliptic. This angular distance is 23.5°, This angle also marks a line of latitude on the Earth called the Tropic of Cancer.
The Tropic of Cancer is so called because the summer solstice used to occur when the Sun was in the constellation Cancer and the latitude lines in the tropical zone. There is also a comparable line of latitude south of the equator called the Antarctic Circle. The latitude is 66.5° South and for anyone living south of this latitude (really, mostly penguins or anyone stationed in Antarctica), the Sun will never rise. Conversely, the Arctic Circle at 66.5° North, the Sun never sets. In fact, from the vernal equinox to the autumnal equinox, the North Pole is in perpetual sunlight, while the South Pole is in perpetual darkness.
The summer solstice marks the day of the year when the northern hemisphere receives the most light. From here on until the winter solstice, the days will only get shorter and the nights longer. In the southern hemisphere, the opposite occurs. Today marks the shortest day of the year and they are in winter time.
21 May 2016
Mars at Opposition
Mars will be at opposition on May 22nd, 2016.
From a previous post, we know that opposition occurs when the planet and the Sun are 180° away from each other in the sky. What this means is that when the Sun is setting, the planet will be rising. In the next couple of days, if you look to the east at sunset, Mars will be rising above the horizon. A great time to view Mars would be at midnight when it is near the apex of its path across the sky. Mars will be in Scorpius (the constellation opposite the Sun's location in Taurus) as seen here.
Because Mars is at opposition, it is the closest to us, but is still about 0.4 AU (60 million kilometers or 37.2 million miles) away from us.
From a previous post, we know that opposition occurs when the planet and the Sun are 180° away from each other in the sky. What this means is that when the Sun is setting, the planet will be rising. In the next couple of days, if you look to the east at sunset, Mars will be rising above the horizon. A great time to view Mars would be at midnight when it is near the apex of its path across the sky. Mars will be in Scorpius (the constellation opposite the Sun's location in Taurus) as seen here.
Because Mars is at opposition, it is the closest to us, but is still about 0.4 AU (60 million kilometers or 37.2 million miles) away from us.
03 May 2016
TRAPPIST-1 Planets
TRAPPIST-1 is an M8 dwarf star which is one of the coldest stars on the Hertzsprung-Russell Diagram. It has a surface temperature of about 2550 K (the Sun, by comparison has a surface temperature of 5800 K) and a mass of approximately 0.08 Solar masses.
Recently, astronomers led by Michael Gillon of the University of Liege announced that they discovered three planets orbiting TRAPPIST-1 using the transit method. The two closest are tidally locked to their parent star, much like the Moon is tidally locked to Earth. However, the third planet lies just at the outer edge or beyond the habitable zone of the star.
Theoretically, this planet could harbor life, but in all likelihood, it would nothing like Earth life. By being in the habitable zone, this means that water would be in liquid form, which astronomers believe would be necessary for life to exist.
Recently, astronomers led by Michael Gillon of the University of Liege announced that they discovered three planets orbiting TRAPPIST-1 using the transit method. The two closest are tidally locked to their parent star, much like the Moon is tidally locked to Earth. However, the third planet lies just at the outer edge or beyond the habitable zone of the star.
Theoretically, this planet could harbor life, but in all likelihood, it would nothing like Earth life. By being in the habitable zone, this means that water would be in liquid form, which astronomers believe would be necessary for life to exist.
02 May 2016
Transit of Mercury
On May 9, 2016, the planet Mercury will transit across the face of the Sun and for most of the Earth, the transit will be visible (or at least portions of it).
The transit begins at 11:12 UTC (Coordinated Universal Time measured at Greenwich, England) and ends at 18:42 UTC. To determine your time offset from UTC, Wikipedia has a good summary. For example, in Pittsburgh (where I live), we are currently only four hours behind UTC due to daylight savings time. So in Pittsburgh, the transit begins at 7:12 AM and ends at 2:42 PM.
To see the transit, you should not look directly at the Sun.. There are a couple of ways to look at it, however.
The transit begins at 11:12 UTC (Coordinated Universal Time measured at Greenwich, England) and ends at 18:42 UTC. To determine your time offset from UTC, Wikipedia has a good summary. For example, in Pittsburgh (where I live), we are currently only four hours behind UTC due to daylight savings time. So in Pittsburgh, the transit begins at 7:12 AM and ends at 2:42 PM.
To see the transit, you should not look directly at the Sun.. There are a couple of ways to look at it, however.
- Have a Sun filter for a telescope, binoculars, or camera.
- Watch it online at NASA.gov.
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