A disadvantage of longitudinal studies is that

Explanation:

unpredictability always present.

Because longitudinal studies involve the same subjects over a long period, what happens to them outside of the data collection moments can influence future data being collected. Some people may choose to stop participating in the research. Others may no longer find themselves in the correct demographics for the research. If these factors are not included in the initial design of the research, then it could invalidate the findings that are produced.

2. It takes time.

Researchers involved with longitudinal studies may never see the full outcome of their work. It may take several years before the data begins producing observable patterns or relationships that can be tracked. That means the ability to maintain open lines of communication with all researchers is vitally important to the eventual success of the study.

3. The data gathered by longitudinal studies is not always accurate or reliable.

It only takes one piece of unreliable or inaccurate data to possibly invalidate the findings that the longitudinal studies produce. Because humans have their own personal bias toward certain subjects, the researcher processing the data may unconsciously alter the data to produce intended results.

4. It relies on the skills of the researchers to be complete.

Because data collection occurs in real-time and relies heavily on the skills of the researchers who are tasked with this job, the quality of the data is heavily reliant on those skills. Two different researchers

light-year  

the distance that light travels in a vacuum in one year, equal to about 9.46 trillion km (5.88 trillion mi). light-years are used in measuring interstellar and intergalactic distances.  

parsec  

a unit of distance used in astronomy, equal to about 3.25 light years (3.08 × 1016 meters).  

parallax  

the apparent angular displacement of a celestial body due to its being observed from the surface instead of from the center of the earth (diurnal parallax or geocentric parallax) or due to its being observed from the earth instead of from the sun (annual parallax or heliocentric parallax)  

absolute magnitude  

the magnitude (brightness) of a celestial object as it would be seen at a standard distance of 10 parsecs.  

apparent magnitude  

the magnitude of a celestial object as it is actually measured from the earth.  

redshift  

an increase in the wavelength of radiation emitted by a celestial body as a consequence of the doppler effect.  

the great thing about your imagination is that it doesn't have to make sense! if i were you i would be stuck in space, no communication with earth travelling around and around, you can only guess how long its been since your communication broke down. you land on an undiscovered planet, you do a scientific investigation examining the elements and conditions. you come across alien lifeforms.  

best of luck!

a.10 children i think